Load an dll class library with autolisp

This tutorial aims to guide for load a dll file with autolisp code
The file dll name, in this sample, is 'Mydll.dll' with class name 'class1'
(Register your dll file for lisp application)
In this case the dll file contains a sample function 'Public Function s_con(ByVal s_first As String, ByVal s_second As String )' (vb.net code)
The sample function 's_con' return a concatenation of first string variable and second string variable.
The autolisp code is: